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Model output discussion - after the beast, what next?


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The UKMO 144 has teased me out if hibernation - for a comment. 144 shows a very meridional flow across 50N with deep cold filtering into Scandi- could be a sharp transition from mild to cold

No mate, I'm still in winter mode as long as the Gfs shows potential arctic blasts..hope it continues!❄❄❄❄❄

Ahhh another chocolate teapot in your post... I believe the last one froze. It seems that we are seeing the second response to the SSW with another surge of negative zonal mean u winds heading fo

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Just now, Purga said:

06z GEFS for London as an example, almost matching the Beast Mark 1.0 levels of cold intensity!

image.thumb.png.5dc5bc2cf638146c65301a8425691599.png

-13 / -14C uppers strongly supported + decent precipitation spikes as well = ❄️❄️❄️

:yahoo:

Yeah Purga exceptional really, The south East has a much greater margin of error regarding coldest uppers and unstable flow, us in the north will be keeping a close eye on the 12z for any more southward corrections 

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Updated swingometers again for 06z with improved colour schemes!

image.thumb.png.34696e0f541eba39ff91bbd20a93a272.png

Considering the 06z ens have shown a few wobblies in the last few days that is a great ens set! However a few have watered down/indirect easterlies but I don't think that looks very likely now.

An improved swingometer I've created shows weather the cold will persist or re-emerge into next week. Or whether it just settles down and temperatures increase under a ridge of high pressure. Here are those results

image.thumb.png.faaee27743028d281f95c4384495a569.png

With the purple runs we would stand a fair chance of seeing a March CET around or under 3C with some notable cold pooling from the north. A little step back from that extreme scenario on the 06z ens but its still a distinct possibility!
 

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Looking at the ensembles Saturday to Monday looks to be the peak period for the cold snap and subsequent chances of snow

gefsens850London0.thumb.png.1d238d13aa66c7955a5d0571910d714e.pnggefsens850Newcastle0.thumb.png.2a2276f89dcddb4bee0dc86ba6d0cbea.pnggefsens850Edinburgh0.thumb.png.96beb75132a2c1248389d1d0953f2db8.png

Note the higher numbers around the period mentioned the closer to 23 the greater the chances of snow

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1 hour ago, bluearmy said:

Now the clusters are out, they look far more amplified in the extended period that the mean/anomolys as these are skewed by a troughy Atlantic cluster and differing timings 

so, I would now agree that a notable mid Atlantic upper ridge is still a well supported extended period option 

the shorter term eps show that there is probably a 50/50 split around the op and something closer to ukmo 

thereafter, so many variations on a theme that you wouldn’t want to be anything other than vague - ie. staying cold with a continuing chance of wintry precip though more likely rain to lower levels and further south 

I think the last cold spell reminded us how the models struggle when deep cold pools appear in places they wouldn't normally be, with the second week in March very late in being resolved. I wouldn't be surprised to see the same here, perhaps with new solutions to the "after the beast part 2" appearing even in two or three days time. 

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Afternoon all :)

Plenty of excitement in the thread as the upcoming cold snap approaches or will it be a cold spell ? Can we get the double "hit" of the E'ly followed by the N'ly or NE'ly via retrogression ? Last time it all happened too quickly and we moved quickly into a west-based negative NAO which allowed the Atlantic back in.

Let's say where we due to be (or at least where the models think we will be) at the end of next week, Friday March 23rd.

Starting with the ECM at T+240:

ECM1-240.GIF?13-12

The weekend cold snap soon receded as the lobe of HP drops and is absorbed into the Azores HP but this in turn is displaced by a shallow LP off the Atlantic which sits well to the west of the British Isles with a trough facing NE toward a more significant LP in the Norwegian Sea. A WSW'ly airflow covers the British Isles but this is returning PM air rather than TM air and a brief milder incursion taking uppers positive is being pushed away by colder air sending uppers back negative so a cold front passing with rain followed by showers and the eye is drawn to the building mid-Atlantic ridge.

On to the GEM 00Z at T+240:

gem-0-240.png?00

A cold or very cold run for the time of the year - about as good as it gets in all honesty. The HP duly retrogresses and the winds shift from East to North leaving a large3 pool of very cold air over Scandinavia. A complex and slow moving trough sits in that cold air and Atlantic LP are being disrupted SE into Europe. An LP to the west of Ireland is negatively aligned and set to move SE into Europe. Uppers over the British Isles are broadly negative with very cold air (below -8 850s) over northern and eastern areas. For most southern and western parts rain would be the call but for northern and eastern areas and especially those with altitude snow seems probable.

GFS 00Z at T+240:

gfs-0-240.png

A halfway house to a point. The original E'ly blast is followed by a short N'ly down the east coast but the HP sinks south as per ECM and is absorbed by the Azores HP which by this stage is itself declining SW as shallow Atlantic systems move in from the NW. Colder air has been driven out of the east and a light W'ly flow covers the British Isles ahead of frontal rain moving in from the north west. Further into FI a mid-Atlantic ridge builds south from Greenland allowing the trough to extend from Europe back over the British Isles so no sign of spring.

GFS 06Z OP at T+234:

gfs-0-234.png?6

Not too dissimilar with the Scandinavian-European (or ScEuro) trough in control and the line between very cold air to the NE and much warmer air to the SW. The trough is negatively aligned taking the energy SE into Europe but with a weak ridge coming in from the west, a transient spell of quieter weather (night frost ?) is on the cards but uppers are broadly negative so the cold is in charge for now - or at least the slightly below average is in charge for now.

Further into FI, the trough disrupts south so we get a cold NE'ly but that fades as Easter approaches but with heights building back to the north, the trough disrupts again and cold air returns again from the east and north east.

GFS 06Z Control at T+240:

gens-0-1-240.png

Broadly similar to the OP with the negatively tilted trough in charge to the west but more in the way of heights over eastern Europe at this time. Further into FI and the trough is split and disrupted as HP builds strongly back across Scandinavia and threatens to join with the Azores HP and a weak European trough to re-introduce much colder air.

The 06Z GEFS at T+240:

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240

A mixed bag as you'd expect but the negatively tilted trough is a strong signal. No sign of anything warmer but no real E'ly either. Yes, there's plenty of weak blocking but more from the NW than the NE by this time. Not much changes further into FI and while there are signals for both mid-Atlantic ridging and renewed Scandinavian blocking neither are that strong and a gentle return to Atlantic dominance would be the welcome albeit that is a GFS "default" according to some.

In conclusion, spring remains firmly on hold this morning, Whatever the details of the coming weekend, however, both GFS and ECM, while not prolonging the weekend's cold, keep the weather decidedly chilly with negatively aligned troughs and colder air never far away and making occasional incursions. GEM looks an outlier but it's about the best chart coldies could want for the time of the year. Both GFS and ECM take the lobe of HP away from Greenland after the weekend and drop it south to the Azores while GEM holds it rather longer closer to Greenland. That's the difference between a cold snap and a cold spell to this observer but let's see where we are tomorrow. 

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8 minutes ago, Man With Beard said:

I think the last cold spell reminded us how the models struggle when deep cold pools appear in places they wouldn't normally be, with the second week in March very late in being resolved. I wouldn't be surprised to see the same here, perhaps with new solutions to the "after the beast part 2" appearing even in two or three days time. 

we have nothing like the same magnitude of -AO/NAO predicted this time so I doubt we are going to see cold pools headed into the mid atlantic to our sw!

the zonal flow is on the turn today at 60N but its a gentle drop from 10 m/s and the reversal in a weeks time is quite gentle. tbh, we are already reversed north of 70 degrees so I don't expect to see the kind of turmoil we saw last time ahead of the scandi high establishing and then the acceleration of the neg NAO being picked up

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1 hour ago, Summer Sun said:

Looking at the ensembles Saturday to Monday looks to be the peak period for the cold snap and subsequent chances of snow

gefsens850London0.thumb.png.1d238d13aa66c7955a5d0571910d714e.pnggefsens850Newcastle0.thumb.png.2a2276f89dcddb4bee0dc86ba6d0cbea.pnggefsens850Edinburgh0.thumb.png.96beb75132a2c1248389d1d0953f2db8.png

Note the higher numbers around the period mentioned the closer to 23 the greater the chances of snow

Good charts for coldies.

Cracking METO text update today btw, cold enduring right through to April - certainly judging by SS's reaction!

image.thumb.png.1edc467a39a5e34cba4c73e93b685c1e.png

:laugh:

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What the?... ?

Haven’t looked at the Models in the last few days as I admit, for my preferences, they didn’t seem to be showing anything that exciting. Only to then come back and find many of them are showing a potent Easterly with -10/11/12/13*C 850 hPa temperatures covering parts of the U.K. for the weekend! ?

Now I know the models have been showing some continued blocking to our North or North-East and a Southerly tracking Jet, but still wasn’t expecting to see that! With that possibility still some days away, things could still change for the worst regarding this weekend’s snowy possibilities (the exact angle and placement of that Scandinavian High, for example, could affect where the cold deepest air heads to). However, it’s amazing what happens when you take a break from the models! 

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Quite a cold set of 2m temp.ens.for London too.

ensemble-tt6-london.gif

Looking notably cold for around 4 days before something of a recovery but still on the cold side.

and the precipitation graph

ensemble-rrrcum-london.gif

Note the spike at the weekend along with a sharp drop in temperature so something is afoot!

 

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4 hours ago, danm said:

Completely agree. 

To be getting these synoptics and depth of cold in mid to late March is exceptional. Solar energy will now be our friend and our foe. It will likely instigate convection further in land but it will also rapidly thaw any exposed lying snow even if temps and dew points are sub zero. John Hammond made a comment on one of his videos yesterday that surprised me actually -  solar energy is apparently now 50% stronger than it was just 2/3 weeks ago at the onset of the last freeze and any deep cold uppers will more quickly get modified by warmer air. 

So a potentially excellent cold snap/spell coming up but unlikely to last long without a further injection of deep cold. Which at this time of year is still excellent. 

i saw exceptional snow in March 2013 that wasn't gone completely from the ground until the end of the second week in April

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52 minutes ago, Timmytour said:

i saw exceptional snow in March 2013 that wasn't gone completely from the ground until the end of the second week in April

Strange - I don’t remember that at all - did you build a 50 foot snowman Timmy ??

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The met office have done a video for the weekend one option on the table is for high pressure to be further south meaning it will be dry with very little snow

567575.thumb.png.a8a40fc42380d53acc644749339bdfcc.png

The second option shows low pressure over Europe to be a bit further north meaning more chance of snow as indicated by the increased amount of crosses

6466sn.thumb.png.28f3d441a96a359c2d0b04d93399c973.png

Whilst the weekend will be cold either way the finer details regarding potential snowfall won't be known for a few more days yet

Edited by Summer Sun
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